Recently, it becomes possible to use various wireless communication access systems due to an advancement in a wireless communication technology. A cellular communication system, such as W-CDMA (Wideband Code Division Multiple Access) or LTE (Long Term Evolution), used as a mobile wireless communication system, WiMAX (Worldwide Interoperability for Microwave Access) based on the IEEE802.16 technology, and a wireless LAN in conformity with the IEEE802.11 technology, may be included as the principal wireless communication systems.
Wireless terminals equipped with a communication interface for communicating with a plurality of wireless communication access systems have been widely distributed in order to meet the demand for mobile communication or due to the advancement in implementation technology of a terminal. A representative wireless terminal includes a smart phone and a tablet PC each includes a dual terminal generally having both wireless communication interfaces for the cellular communication system and the wireless LAN. The dual terminal generally selects and uses any one of the wireless access channels of the cellular communication system and the wireless LAN according to the quality of radiowave in the respective wireless access channels. In the meantime, a technology has been emerged that enables a higher speed communication through the concurrent use of a plurality of different wireless access channels. See, for example, Japanese Laid-Open Patent Publication No. 2011-142602, No. 2009-246875, and No. 2011-61253.
FIG. 1 illustrates a block diagram of an exemplary configuration of a conventional wireless communication system. In FIG. 1, an interface 11 at core network side of a base station apparatus 10 is coupled with a core network to transmit/receive communication data to/from the core network. A virtual MAC processing unit 12 performs a processing for establishing a link using a virtual MAC address and establishes a link with a virtual MAC processing unit 22 using the virtual MAC address. Further, the virtual MAC processing unit 12 generates a frame to be transferred using the link. A switching unit 13 distributes link frames sent from the virtual MAC processing unit 12 to each wireless module 14a, 14b, 14c, and outputs the link frames supplied from each wireless module 14a, 14b, 14c to the virtual MAC processing unit 12.
The macrocell wireless module 14a performs a wireless communication with a macrocell wireless module 24a of a mobile station device 20 through the 3G (3rd Generation) or LTE. The macrocell wireless module 14b performs a wireless communication with a macrocell wireless module 24b through the WiMAX. The picocell wireless module 14c performs a wireless communication with a picocell wireless module 24c through the wireless LAN. A wireless environment recognition unit 15 recognizes the wireless environment and indicates a destination to which a link frame, which is input from the virtual MAC processing unit 12, is to be distributed, to a switching unit 13 based on the recognition result.
The mobile station device 20 serving as a wireless terminal apparatus employs substantially the same configuration as the base station apparatus 10. An interface 21 at a user network side of the mobile station device 20 performs a processing for a network layer. Further, the mobile station device 20 includes, but is not limited to, a virtual MAC processing unit 22. The mobile station device 20 controls the switching unit 23 to select an optimum wireless module from the wireless modules 24a, 24b, 24c based on information such as the communication quality acquired by a wireless environment recognition unit 25.
FIG. 2 illustrates the configuration in which a plurality of wireless access systems are coupled with each other to form a network. In FIG. 2, a WiFi access network 33 is coupled to a cellular network constituted with a macro wireless access network 31 and an operator core network 32. In FIG. 2, a wireless terminal apparatus 34 accesses the macro wireless access network 31 as well as the WiFi access network 33 through the wireless access channel of, for example, the W-CDMA. Also, the wireless terminal apparatus 34 may set two connections using a mobile IP technology, that is, one connection to the macro wireless access network 31 via a path from an HA (Home Agent) 35, which belongs to the operator core network 32, and the other connection to the WiFi access network 33 via another path from the HA 35, thereby making traffic flows that are different from each other to pass through.
Further, in addition to a macro base station installed at a building rooftop or a steel tower to cover an area with the radius of several kilometers, a femtocell base station which is installed in an indoor of, for example, a house to cover an area with the radius of about 10 meters is being distributed in the cellular communication system. A product in which a wireless LAN interface is equipped in the femtocell base station makes an appearance as well.